The present invention relates to tube cleaning and particularly to launching tube cleaning projectiles by pressurized water through heat exchanger tubes for cleaning tube interior surfaces so as to maintain thermodynamic efficiency, to extend tube life, and to clear away deposits that constrict fluid flow through the tubes.
Shell and tube heat exchangers comprise a bundle of tubes with ends mounted to tube sheets that close each end of the shell. In normal operation, hard deposits such as rust and scale containing calcium, and soft deposits including slime and loose dirt build up on the interior surface of the tubes so as to diminish thermal efficiency and restrict fluid flow through the tubes. To maintain thermal efficiency and design flow in operation of the heat exchanger, it is necessary to remove such deposits on a regular maintenance schedule.
These deposits are removed mechanically by means of a tube cleaning projectile or plug driven through the tube by pressurized media including air, water, steam, or other gas. The projectile outer diameter is greater than tube bore diameter and the projectile surface is fitted with cleaning elements including brush and scraper components configured for effective cleaning of the interior wall. The projectile forms a seal against the interior wall such that the full force of the fluid pressure acts to move the projectile through the tube. Preferably, the projectile pushes removed deposits ahead through the tube so both projectile and deposits are ejected from the far end of the tube in an exhaust stream of propelling media.
Hand held devices of the type described in Thompson U.S. Pat. No. 1,806,270 are used to position a plug for entry into a heat exchanger tube, and to propel the plug through the conduit with fluid pressure, typically, compressed air. The plugs preferred by Thompson are of a resilient nature and are preferably made of rubber. Strasburg U.S. Pat. No. 1,808,870 uses compressed air to clean condenser tubes by propelling rubber balls through the tubes. Oberhuber U.S. Pat. No. 1,867,751 discloses a gun with trigger operated valve for driving condenser cleaning slugs through tubes utilizing steam, water, or high pressure air. Wallace U.S. Pat. No. 3,451,091 discloses a device for cleaning tubes of boilers, condensers and heat exchangers utilizing a plug formed from conventional rope fed from a coil with its free end wrapped, inserted into a tube end, severed from the body of the rope, and forced through the tube by air or steam supplied through a handle.
The present invention is directed to improvements in launchers and devices for tube cleaning by propelling projectiles, plugs and the like to brush or scrape deposits from the interior surface of the substantial number of tubes comprising a heat exchanger, and doing so in an economic plant maintenance program.